Aug. 27, 2010 -- Breastfeeding for a month or longer appears to reduce a woman's risk of getting diabetes later in life, according to a new study.

The breastfeeding and diabetes link has been reported in other studies, according to researcher Eleanor Bimla Schwarz, MD, assistant professor of medicine at the University of Pittsburgh School of Medicine.

Her study lends more credence to the link, she says. "Moms who had ever breastfed were much less likely to develop diabetes," Schwarz tells WebMD. ''Moms who had never breastfed had almost twice the risk of developing diabetes as moms who had."

The study is published in The American Journal of Medicine. It was funded by the National Institute of Diabetes and Digestive and Kidney Diseases and the National Institute of Child Health and Development.

Breastfeeding and Diabetes: A Closer Look

Schwarz and colleagues looked at data gathered for another study on risk factors for incontinence, evaluating information given for that study on breastfeeding practices and whether the women later developed diabetes. The women were ages 40 to 78 and all members of a large health maintenance organization in California.

The researchers evaluated data on 2,233 women. Of those, 405 were not mothers, 1,125 were mothers who breastfed for at least a month, and 703 were mothers who had never breastfed.

The risk of getting a diagnosis of type 2 diabetes for women who breastfed all their children for a month or longer was similar to that of women who had not given birth.

But mothers who had never breastfed were nearly twice as likely to develop diabetes as women who had never given birth.

Moms who never exclusively breastfed were about 1.4 times as likely to develop diabetes as women who breastfed exclusively for one to three months, Schwarz found.

Later in life, here is the breakdown of who developed diabetes:

17.5% of the women who hadn't given birth.

17% of the women who breastfed all their children for a month or longer.

20.3% of those who breastfed, but not all children for a month or longer.

26.7% of moms who didn't breastfeed.

Overweight and obesity were common among the participants, with 68% having a body mass index of 25 or more, considered outside the healthy weight range.

The link held, Schwarz says, even after controlling for factors such as weight, physical activity, and family history of diabetes.

While one month of breastfeeding appears to make a difference, Schwarz says even longer is better. "Previous studies have shown the longer the mom breastfeeds, the more benefit for your body."

Many experts recommend exclusive breastfeeding for six months and continuing [supplemented by food] for a year," she says. "Clearly it's hard for moms to always negotiate breastfeeding given the constraints of their work environment," she tells WebMD.

Breastfeeding and Diabetes: Explaining the Link

The diabetes-breastfeeding link is probably explained by belly fat, Schwarz says. Moms who don't breastfeed, as they get older, may have more belly fat, she says, as breastfeeding helps new mothers take off weight. "Belly fat increases the risk of diabetes as you get older."

Some research has shown that breastfeeding may increase sensitivity to insulin, in turn reducing diabetes risk. But that may be short-term -- while the breastfeeding is occurring, Schwarz says. "The real problem may be the belly fat."

She often counsels women who get gestational diabetes (occurring during pregnancy) that they are at risk for later getting type 2 diabetes and suggests they breastfeed.

The new findings, Gregory tells WebMD, will probably inspire her to add to the advice she gives moms-to-be about the benefits of breastfeeding. She often focuses on the benefits to the baby during that discussion, says Gregory, a professor of obstetrics and gynecology at the University of California Los Angeles School of Public Health.

But with the new research, she says, she may expand on that discussion. "I think it would make me say, 'Oh by the way, breastfeeding would also help you lose your weight faster and could possibly decrease your likelihood of becoming diabetic later in life."

SOURCES: Eleanor Bimla Schwarz, MD, assistant professor of medicine, University of Pittsburgh School of Medicine.

Schwarz, E. The American Journal of Medicine, September 2010; vol 123: pp 863.e1-6.